This invention may be described as a fluid assisted wedging and compacting device which is used to lay cable underground by wedging and compacting an opening and simultaneously laying cable in the soil and is designed to provide high pressure water through the wedging face of a blade to improve overall wedging efficiency.
The present invention relates to a device for installing cable underground and more particularly to a specifically designed wedging and compacting blade arrangement for use in such device.
Present devices used for installing cable consist primarily of a vertical blade attached to a boom of a power driven land vehicle. The land vehicle is equipped with one or more cable spools to supply cable to a cable feed tube, typically installed behind the blade. The blade can be of various lengths and has a wedging surface on the front half to wedge an opening in the soil. The blade is typically connected to a hydraulically operated boom that lowers the blade into soil to a preselected depth wherein the vehicle drags the blade a specified distance. To prevent the shoe from being dragged upward out of the ground, a toe is typically connected to the bottom of the blade which causes the blade to dig deeper, counteracting the blades tendency to pull out of the ground. To prevent the blade from diving too deep into the soil, a shoe can be placed at the top of the blade. The shoe rides along the surface of the soil maintaining a constant blade elevation. To increase the wedging effectiveness of the blade, a vibratory device can be installed on the blade mount to vibrate the blade while it wedges through the soil. As the blade wedges a trench in the soil, the cable feed tube, which is typically pivotally attached to the rear of the blade, guides one or more cables into the freshly wedge trench. When wedging dry dense clay soil, it becomes difficult or impossible to drag the blade and rate of speed high enough to be considered commercially useful. In order to wedge through clay, it is necessary to wedge incrementally, making several passes with the blade until the desired depth is achieved. To further increase the wedging effectiveness of the blade when the soil is hard and dense, it has been found that the addition of high pressure water jets attached to the blade aid in wedging through the soil. An example of a wedging and compacting apparatus that uses high pressure water can be found in U.S. Pat. No. 4,498,813, entitled UNDERGROUND CABLE INSTALLING APPARATUS AND METHOD UTILIZING A FLUID JET ASSISTED, VIBRATING BLADE ARRANGEMENT. This reference utilizes high pressure water jet nozzles located on the wedging edge of the blade to aid in wedging through the soil. It has been found that nozzles positioned along the wedging edge of the blade, as in the ""813 reference, provide little gain in wedging speed. Actual testing of a blade with water jet nozzles placed along the wedging edge of the blade did very little to increase the wedging rate due to the blocking of the nozzles. The forward movement of the wedging and compacting blade forces the wedging edge of the blade into the clay, blocking the lower nozzles, eliminating the aid of the water on the lower section of the blade, where it is needed most. This reference as well as other prior art devices do not provide for a wedging and compacting device that can be dragged through hard dense clays and a commercially useful rate of speed.
This invention may be described as a fluid assisted wedging and compacting device that enhances the wedging characteristics of the blade, allowing the device to wedge an opening in the soil at a greater rate of speed, reducing the amount of power required to move the blade. The wedging and compacting device is comprised of a blade with high pressure water jet nozzles, a blade toe, a ground shoe and a cable feed tube. The wedging and compacting device is of a vertical arrangement and has a forward facing blade and a connector to allow for pivotal attachment of the cable feed tube. The forward facing blade includes a sharpened blade cutting edge and a blade cutting face located on either side of the edge. The high pressure jet nozzles are placed within a vertically extending groove located on the face of the blade. Directly in front of the groove is an elongated deflector that protects the groove and nozzles from becoming compacted with soil when the blade is dragged forward. It has been found through experimentation that the placement of the high pressure water jets within a groove near the rear of the face of the blade in combination with the protection provided by the deflector, greatly enhances the wedging effectiveness of the high pressure jet nozzles, typically doubling the wedging rate. It has been found that when the blade of the present design is dragged through the soil, a void is created behind the deflector preventing dirt from blocking off the nozzles. Nozzles placed along the wedging edge of the blade, as shown in the prior art, have been found to be ineffective because the pressure of the forward movement of the blade against the dense soil prevents the expulsion of water out of the nozzles. The placement of the jet nozzles in a perpendicular orientation along the face of the blade erodes and softens the soil on the sides of the blade, increasing the overall width of the trench and providing a lubrication to reduce the frictional forces on the wedging and compacting device and feed tube as they are dragged through the soil.